1. Field of the Invention
The present invention relates to an on-demand ink jet head utilizing piezoelectric elements, and more particularly to such a head wherein a plurality of the nozzles are tightly arranged in confrontation with the piezoelectric elements.
2. Description of the Prior Art
An example of conventional ink jet head is illustrated in FIG. 1. As shown therein, piezoelectric elements 4 are in alignment with one another in a columnar direction orthogonal to a main scanning direction. The piezoelectric elements 4 have one end secured to a head substrate 6 and another end attached to a diaphragm 3 by an adhesive material 11. Pressurizing chambers 1 are formed in association with the piezoelectric elements 4, which chambers are defined by a nozzle plate 14 formed with nozzles 1 and a chamber plate 13. Ink is supplied from a common ink channel (not shown) into the pressurizing chambers 1 through individual ink channels defined by the restricting plate 12 and the diaphragm 3.
Referring again to FIG. 1, bonding of the piezoelectric elements 4 and the diaphragm 3 is performed in such a manner that the piezoelectric elements 4 with a predetermined amount of adhesive material 11 coated on the end surfaces thereof are pressed against the diaphragm 3. An excess amount of the adhesive material 11 is then expelled out of the space between the end surface of the piezoelectric element and the diaphragm 3. The flowed out adhesive material 11 is confined in a space between the adjacent two piezoelectric elements 4. Hence, when the adhesive material 11 is solidified, the intervened piezoelectric elements are supported by the solidified adhesive material layers of substantially the same shape. However, with respect to the two endmost piezoelectric elements, the solidified adhesive material layer in the outer side is different in shape from that in the inner side. The solidified adhesive material 11 has elasticity and serves as dampers of the piezoelectric elements 4.
When printing is performed with the ink jet head thus constructed, a secondary droplet is occasionally ejected following ejection of a primary droplet. The two droplets do not overlap when they impinge on a recording medium.